Field of the Invention
The present invention relates to a multicomponent gear.
Background of the Invention
A multi component gear of this type, as is used for example for electric steering of motor vehicles, is known from EP 1 777 439 B1. This multicomponent gear consists substantially of three components. The actual toothed rim is formed by an outer part, which consists of plastic and has a multitude of teeth for forming the toothed rim. The toothed rim has on the inner side an insert part 3, which is conventionally formed as a hub or shaft. This inner part thereby consists generally of metal, preferably steel. The outer part with the toothed rim thereof and the inner part are connected to each other in a positive locking way via a connecting part, which is produced by cone gate injection molding. The connecting part, injection molded of plastic, has reinforcing ribs on the two opposite primary surfaces thereof, i.e. the exterior annular surfaces lying perpendicular to the rotational axis, which ribs extend in the radial direction from the conceived center of the rotational axis, starting from the inner part in the direction of the outer part and thus to the toothed rim. In addition, the two primary surfaces of the connecting part have an annular reinforcing ring facing the inner part and a further reinforcing ring facing the outer part. The reinforcing ribs extend radially between these two reinforcing rings. If a radial section through this connecting part is viewed between the aforementioned reinforcing ribs, then an H-shaped cross sectional contour of the circumferential connecting part is shown.
DE 101 27 224 A1 also discloses different embodiments of multicomponent gears. FIG. 8 thereof likewise shows a multicomponent gear having an inner metal hub and a toothed rim made of plastic, wherein this toothed rim is connected to the metal hub via a plastic disk having reinforcing ribs arranged on both primary surfaces. FIG. 10 thereof also shows a connecting part designed with an H-shape in cross section.
It has become apparent that multicomponent gears of this type are in need of improvement, in particular when only limited installation space and in particular when a limited gear width is available and despite this a gear that is axially as rigid as possible must be provided. Ideally, a very axially rigid gear could be provided by a gear body made of solid material. This fails, however, when using plastic in the production process. Namely, the production of thick-walled plastic bodies has the problem of cavity formation. This is understood to mean the occurrence during injection molding of plastics of undesired hollow spaces in the inside of an injection molded workpiece or dents on the surface thereof. The thicker the walls of an injection molded workpiece, the higher the likelihood that this type of cavities will occur. It would indeed be theoretically possible to form the inner part with an H-cross section. For rotationally symmetrical wheel bodies, like gears, however, a cross section of this type cannot be implemented, as the corresponding hollow spaces cannot be injected.
The goal of the invention is to provide a multicomponent gear which uses relatively little material and despite this is distinguished by a high axial rigidity.